3GPP LTE (3rd generation partnership project long term evolution) and LTE-A (LTE-advanced) will now be described as an exemplary mobile communication system to which the present invention is applicable.
FIG. 1 illustrates E-UMTS (evolved universal mobile telecommunication system) as an exemplary mobile communication system.
E-UMTS evolved from UMTS (universal mobile telecommunication system) is currently standardized in 3GPP. E-UMTS may be regarded as an LTE system. For technical specifications of UMTS and E-UMTS, reference can be made to Release 8 and Release 9 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.
Referring to FIG. 1, E-UMTS includes a user equipment (UE), a base station (BS) and an access gateway (AG) located at the end of a network (E-UTRAN) and connected to an external network. The BS can simultaneously transmit multiple data streams for multicast service, and/or unicast service.
One or more cells are present in a BS. A cell is set to one of bandwidths of 1.25, 2.5, 5, 10, 15 and 20 MHz and provides downlink or uplink service to a plurality of UEs. Different cells may provide different bandwidths. The BS controls data transmission/reception to/from a plurality of UEs. The BS transmits downlink scheduling information about downlink data to the UE to inform the UE of a time/frequency region in which data will be transmitted, coding, data size, hybrid automatic repeat and request (HARQ) related information, etc. In addition, the BS transmits uplink scheduling information about uplink data to the UE to inform the UE of a time frequency region that can be used by the UE, coding, data size, HARQ related information, etc. An interface for user traffic or control traffic transmission may be used between BSs. A core network (CN) may be composed of a network node for user registration of the AG and UE. The AG manages mobility of the UE for each tracking area (TA) composed of a plurality of cells.
While wireless communication technology has been developed to LTE on the basis of wideband code division multiple access (WCDMA), demands and expectations of users and service providers continuously increase. Furthermore, new wireless access technologies are continuously developed, and thus technical evolution is needed to achieve competitiveness. That is, reduction in cost per bit, service availability increase, flexible use of frequency bands, simple structure and open interface, appropriate power consumption of a UE, etc. are required.
Recently, 3GPP has performed standardization of follow-up technology regarding LTE. This technology is called ‘LTE-A’ in the specification. LTE and LTE-A differ mainly in terms of system bandwidth and introduction of a relay.
LTE-A is aimed at supporting a wideband of up to 100 MHz. To achieve this, carrier aggregation or bandwidth aggregation that accomplishes a wideband using a plurality of frequency blocks is used.
Carrier aggregation uses a plurality of frequency blocks as a wide logical frequency band in order to use a wider frequency band. The bandwidth of each frequency block can be defined based on the system block bandwidth used in LTE. Each frequency block is transmitted using a component carrier.
Although new control channels are considered for LTE-A, how to design and transmit the control channels has not been researched yet.